Blob Structure and Motion in the Edge of NSTX

Authors:  S.J. Zweben, J.R. Myra, W.M. Davis, D.A. D'Ippolito, T.K. Gray, S.M. Kaye, B.P. LeBlanc, R.J. Maqueda, D.A. Russell, D.P. Stotler and the NSTX-U Team

Abstract:  The structure and motion of discrete plasma blobs (a.k.a. filaments) in the edge and scrape-off layer (SOL) of NSTX is studied for representative Ohmic and Hmode discharges. Individual blobs were tracked in the 2-D radial vs. poloidal plane using data from the gas puff imaging (GPI) diagnostic taken at 400,000 frames/sec. A database of blob amplitude, size, ellipticity, tilt, and velocity was obtained for ~45,000 individual blobs. Empirical relationships between various properties are described, e.g. blob speed vs. amplitude and blob tilt vs. ellipticity. The blob velocities are also compared with analytic models.

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Submitted to:  Plasma Physics and Controlled Fusion
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Download PPPL-5194 (pdf 4.3 MB 48 pp)
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